Filter material



Nov. 20, 1945. R. KARLSTRM FILTER MATERIAL Filed Jan. 26, 1943 MAM NVENTOR WQBYyVr/'rmw ATTORNEY Patented Nov. 20, 1945 FILTER MATERIAL Robert Karlstrm, Stockholm, Sweden, assgnor to Electrolux Corporation, Old Greenwich, Conn., a corporation of Delaware Application January 26, 1943, Serial No.Y l173,609 In Sweden July-9, 1942 s claims. l(Cl. '18s-e9) present invention relates to a filter material for fluid, such as air, and more particularly to a Vmaterial of this kind which is efficient but at the same time cheap to manufacture. The material referred to may suitably be used for filteringair in vacuum cleaners, and satisfies high demands as to great separating capacity and low resistance to flow. Owing toits low cost 'of manufacture' the filter material, when used as a vacnum `cleaner filter, whether formed as a plane hltef' o1 a; so-called dust bag, may be thrown away or burnt after a certain period of use, in the latter case together with the separated impuritles collected in the bag. If desired, material in aboordance with the invention may be used in connection with a filter of another kind, such as a textile filter, or may replace such a filter. The new filter material has great strength, which is necessary particularly in the case of bag-like ltfs' intended for vacuum cleaners and, when in use, subjected to continuous deformations. According to the invention the filter material consists of at least two layers, namely a supportlayer arid a filter layer, lying close against eachother' and forming a unit, the opposite surfaces offsa'id layers adhering to each other. In a suitable embodiment of the invention a binding agent is vintroduced between the layers so as to cause them to adhere to each other. If desired, lthe Ymaterial containedv in one or more of the may itself be of such a quality that merely bringing it -'into.contact with another .layer will cause it to adhere to the latter. In this latter case it is not thus necessary to introduce any special binding .agent between the layers. The supportim; layer may suitably consist of perforated paper or other air-,pervious material, and the filter layer may consist of a fibrous material stuck to one side of the paper between perforations. These fibers consist for instance of a vegetable material, such as cotton, animal hair, synthetic material.

In a method of manufacturing filter material according to the invention referred to the supporting layer suitably consisting of paper may rst be perforated, whereupon a binding agent and then fibrous material are applied to one of its sides. In another method of manufacturing filter material accordingv to the invention a pulp of fibrous material washed in a glue solution may be received on a wire screen, according to the Fourdrinier process, and applied to the perforated supporting layer, or a fibrous material washed in a glue solution may be applied to the supporting layer which is then perforated.

The accompanying drawing shows diagrammatically three embodiments of the invention on a conside'rably enlarged scale, and in the following description of these embodiments also other characteristics of the invention will be set` forth.

Fig. 1 shows in section an embodiment of a filter material according to the invention in which the supporting layer is undulated, whereas the filter layer is plane.

Fig. 2 shows in section a-iilter material in which the supporting layer is plane, whereas the filter layer is undulated.

Fig. 3 shows a section of a filter layer in which both the supporting and filter layers are plane.

Inthe drawing the supporting layer is, in all figures, designated by I Il', and the filter layer by I I.

Fig. 1 shows a filter material in which the supporting layer I0 is perforated prior to the appli'- cation of the filter layer II. The supporting layer is shaped so as to have elevations I2=and depressions I3, as seen from the side facing the filter layer. If desired, the perforation of the supporting layer may bev effected simultaneously with the shaping in such a manner that openings I4 are made in the bottom of the depressions I3. If desired, the shaping may be performed Aprior to the perforation. The points cf the elevations I2 are now provided with an adhesive, whereupon the filter layer II which, in this case is made planc, is applied. As appears from the drawing, this will form hollow spaces I5 limited partly by the walls of the elevations I2 and the depressions I3, and partly by the underside of the filter layer.

In the embodiment according to Fig. 2 the perforation of the supporting layer l0 and the shaping of the filter layer II are made separately, whereupon the points of the lter layer designated Vby I6 are provided with a binding agent. The two layers are then assembled in such a manner that said points will bear approximately against the middle of that portion of the supporting layer I0 which is between the perforations I4. The depressions of the filter layer II are designated by I'I and the hollow spaces limited by said depressions and the supporting layer by I8.

In the embodiment shown in Fig. 3 the perforation of the supporting layer I0 is made after the application of the filter layer Il. The perforation or punching of the supporting layer is effected without the use of any cushion, the filter layer II serving as a support. The portions of the supporting layer corresponding to the perforations I4 are designated by I9 and are, during punching, pressed into the material of the 

